/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.update.processor;

import java.io.IOException;

import org.apache.solr.common.SolrException;
import static org.apache.solr.common.SolrException.ErrorCode.*;
import org.apache.solr.common.SolrInputDocument;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;
import org.apache.solr.update.AddUpdateCommand;

/**
 * <p>
 * Base class that can be extended by any
 * <code>UpdateRequestProcessorFactory</code> designed to add a default value to
 * the document in an <code>AddUpdateCommand</code> when that field is not
 * already specified.
 * </p>
 * <p>
 * This base class handles initialization of the <code>fieldName</code> init
 * param, and provides an {@link DefaultValueUpdateProcessor} that Factory
 * subclasses may choose to return from their <code>getInstance</code>
 * implementation.
 * </p>
 */
public abstract class AbstractDefaultValueUpdateProcessorFactory extends
		UpdateRequestProcessorFactory {

	protected String fieldName = null;

	@SuppressWarnings("unchecked")
	@Override
	public void init(NamedList args) {

		Object obj = args.remove("fieldName");
		if (null == obj && null == fieldName) {
			throw new SolrException(SERVER_ERROR,
					"'fieldName' init param must be specified and non-null");
		} else {
			fieldName = obj.toString();
		}

		if (0 < args.size()) {
			throw new SolrException(SERVER_ERROR, "Unexpected init param(s): '"
					+ args.getName(0) + "'");
		}

		super.init(args);
	}

	/**
	 * A simple processor that adds the results of {@link #getDefaultValue} to
	 * any document which does not already have a value in
	 * <code>fieldName</code>
	 */
	protected static abstract class DefaultValueUpdateProcessor extends
			UpdateRequestProcessor {

		final String fieldName;

		public DefaultValueUpdateProcessor(final String fieldName,
				final UpdateRequestProcessor next) {
			super(next);
			this.fieldName = fieldName;
		}

		@Override
		public void processAdd(AddUpdateCommand cmd) throws IOException {
			final SolrInputDocument doc = cmd.getSolrInputDocument();

			if (!doc.containsKey(fieldName)) {
				doc.addField(fieldName, getDefaultValue());
			}

			super.processAdd(cmd);
		}

		public abstract Object getDefaultValue();
	}
}
